Thread-rolling die



June 8, 1943. 1 ERDMAN 2,321,375

THREAD-ROLLING DIE Filed July 18, 1942 IN V EN TIOR.

F/G HARVEY CTfPDMA/Y Patented June 8, 1943 UNETED STATES THREAD-ROLLING ma Application July 18, 1942, Serial No. 451,450

5 Claims.

This invention relates to thread-rolling dies for rolling one or more threads on a novelly formed combined screw and rivet, the thread or threads of which are so formed as to provide a back-out preventing shoulder at the upper end of each thread preferably formed as a continuation of the same which shoulder is adapted to engage the under surface of a work piece to prevent withdrawal of the combined screw and rivet.

The device which is produced by the threadrolling dies of this invention is preferably a selftapping screw which is designed particularly for screwing through a pair of sheets or plates accessible from one side only. The shoulder or shoulders referred to are located a predetermined distance from the head of the screw equivalent to the combined thickness of the sheets to be joined so that when the screw with its threaded part and the shoulder is driven home, the shoulder prevents the device from screwing out of the work by reverse rotation.

For convenience, the device adapted to be formed by the dies of the present invention will be referred to as a scrivet inasmuch as it is the equivalent of a screw and a rivet. V

The principal object of the present invention is to provide thread-rolling dies which will form the thread and arresting shoulder on the scrivet in an efiicient and economical manner.

The invention may be further briefly summarized as consisting in certain novel details of construction and combinations and arrangements of parts which will be described in the specification and set forth in the appended claims.

Although the invention may be utilized in forming a scrivet having one or more threads, for convenience I have shown in the accompanying sheet of drawings dies provided with grooves for forming a scrivet having two threads.

In the accompanying sheet of drawings,

Fig. 1 is an edge view of the dies showing the same in the act of rolling threads on the scrivet;

Fig. 2 is a face View of one of the dies;

Fig. 3 is an enlarged View of a section of one of the dies;

Fig. 4 is a view showing on an enlarged scale the scrivet employed for holding two work pieces together; and

Fig. 5 is an enlarged elevation showing one of the scrivets in its preferred form.

Referring now to the drawing, l and II represent a pair of thread-rolling dies for rolling the thread on a scrivet l2, the die ll) being the movable die and the die H the stationary die.

By referring to Fig. 2 which shows the inner side of one of the dies, it will be seen that each die 'has thread-rolling grooves l3 composed of two portions including parallel portions l3a and shoulder forming portions l3b which extend in a plane parallel to the edge of the die and at a suitable distance therefrom, depending upon the thickness of the two pieces of stock or work sheets to be clamped together. As is customary, the dies has on the starting portion thereof deformations M which insure the desired or correct rolling of the scrivet blank between the dies.

These dies form a scrivet l5 shown in Fig. 4, the scrivet having a pair of threads I 5a and each thread having a shoulder l5b which is located a predetermined distance |5c from the underside of the head lid to receive between the head and the shoulders a pair of work sheets 16 and to clamp them firmly between the head l5d and the shoulders l5b, as shown in Fig. 5. It will be understood that the dies may be employed' for rolling one, two or more threads on the scrivetby varying the distance between the parallel portions [30. of the grooves l 3.

It will be noted by reference to Figs. 4 and 5 that the end of the thread is slightly turned down toward the free end of the shank of the scrivet.

This is accomplished by suitably shaping the end of the groove forming the shoulder [5b. This is shown clearly in Fig. 3 wherein the upper portion I30 of the end of the shoulder forming portion l3b of the groove l 3 is made shorter than the lower portion [3d which is formed parallel with the portion I3a of the groove 13.

It will be observed that these downturned portions of the threads at the ends of the shoulder l5b of the scrivet assist the shoulders l3?) in effectively preventing the withdrawal of the scrivet by turning it in the reverse direction.

Thus it will be seen that I have provided a novel form of thread-rolling die which functions in a new and useful manner. The thread which is formed is preferably, as stated above, a self-tapping thread, but whether or not it is designed for self-tapping depends upon the relative hardness of the scrivet and of the material through which it is to pass.

While I have described the preferred embodiment of the invention, I do not desire to be confined to the precise details shown but aim in my claims to cover all modifications which do not involve a departure from the spirit and the scope,

of the invention.

Having thus described my invention, I claim:

1. A thread-rolling die having a plurality of thread-forming groove which extend diagonally across the die in parallel relation, said grooves at a predetermined distance from the edge of the die being turned laterally with respect to the main portions of the grooves.

2. A thread-rolling die having a plurality of parallel grooves which extend diagonally across the die and which at a predetermined distance from the edge of the die are bent laterally parallel to said edge.

3. A thread-rolling die having a plurality of parallel grooves extending diagonally toward an edge of the die and at a predetermined distance from said edge having portions which are of substantially the same configuration as the parallel with respect thereto.

4. A thread-rolling die having a plurality of V-shaped grooves extending diagonally of the die, said grooves having V-shaped laterally bent portions which extend in the same plane at a predetermined distance from the edge of the die.

5. A thread-rolling die having a plurality of V-shaped grooves extending diagonally of the die, said grooves having V-shaped laterally bent portions which extend in the same plane at a prede- 10 termined distance from the edge of the die, said bent portions terminating in V-shaped ends one side of which is longer than the other.

HARVEY C. ERDMAN. 

